Many different kinds of multi-layer plastic film are required for present day purposes. However, it is not possible to satisfactorily produce such different kinds of multi-layer plastic film with one kind of die. For example, the annular co-extrusion die described and claimed in U.S. Pat. No. 5,690,972 (Planeta et al.) issued Nov. 25, 1997, the contents of which are hereby incorporated herein by reference, is very useful because such a die is easy to take apart and clean and also has a relatively low wetted surface area compared to other dies of similar size.
However, the die described in the above patent is not as suitable as is currently desired for producing multi-layer tubular film which includes at least one layer of material which has poor flow characteristics. It is therefore an object of this invention to provide an annular co-extrusion die which has a similar versatility as the die described in the above patent, but which is especially suitable for producing tubular multi-layer film with at least one layer of material with poor flow characteristics.